U.S. patent application number 15/055422 was filed with the patent office on 2017-06-08 for transformers with multi-turn primary windings for dynamic power flow control.
The applicant listed for this patent is Smart Wires Inc.. Invention is credited to Joe Carrow, Debrup Das, Ali Farahani, Haroon Inam, Amrit Iyer, Arthur Kelley, David Munguia.
Application Number | 20170163036 15/055422 |
Document ID | / |
Family ID | 58799288 |
Filed Date | 2017-06-08 |
United States Patent
Application |
20170163036 |
Kind Code |
A1 |
Munguia; David ; et
al. |
June 8, 2017 |
Transformers with Multi-Turn Primary Windings for Dynamic Power
Flow Control
Abstract
Active impedance-injection module enabled for distributed power
flow control of high-voltage (HV) transmission lines is disclosed.
The module uses transformers with multi-turn primary windings,
series-connected to high-voltage power lines, to dynamically
control power flow on those power lines. The insertion of the
transformer multi-turn primary is by cutting the line and splicing
the two ends of the winding to the ends of the cut high-voltage
transmission line. The secondary winding of the transformer is
connected to a control circuit and a converter/inverter circuit
that is able to generate inductive and capacitive impedance based
on the status of the transmission line. The module operates by
extracting power from the HV transmission line with the module
floating at the HV transmission-line potential. High-voltage
insulators are typically used to suspend the module from
transmission towers, or intermediate support structures. It may
also be directly suspended from the HV transmission line.
Inventors: |
Munguia; David; (San Jose,
CA) ; Iyer; Amrit; (San Leandro, CA) ; Inam;
Haroon; (San Jose, CA) ; Carrow; Joe;
(Oakland, CA) ; Das; Debrup; (Union City, CA)
; Kelley; Arthur; (Napa, CA) ; Farahani; Ali;
(Orange, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Smart Wires Inc. |
San Francisco |
CA |
US |
|
|
Family ID: |
58799288 |
Appl. No.: |
15/055422 |
Filed: |
February 26, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62264739 |
Dec 8, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01F 27/2823 20130101;
H02J 3/1807 20130101; Y02E 40/30 20130101; H05K 7/14 20130101; H02J
3/18 20130101; Y02E 40/50 20130101; H02J 3/26 20130101; H01F 27/29
20130101 |
International
Class: |
H02J 3/18 20060101
H02J003/18; H01F 27/29 20060101 H01F027/29; H05K 7/14 20060101
H05K007/14; H01F 27/28 20060101 H01F027/28 |
Claims
1. A transformer comprising: for use in a series-connectable
distributed active impedance injection module for use in
high-voltage transmission lines; a transformer core; a
multiple-turn primary winding on the transformer core; a
multiple-turn secondary winding on the transformer core; the
multiple-turn primary winding being adapted for splicing in series
with the high-voltage transmission line, the multiple-turn
secondary winding being adapted for connecting to a converter; the
multiple-turn primary winding increasing a voltage injection
capability of a distributed active impedance injection module.
2. The transformer of claim 1 wherein the transformer core is a
non-gapped transformer core.
3. The transformer of claim 1 wherein the multiple-turn secondary
is also adapted for connecting to a shorting switch.
4. The transformer of claim 1 wherein the multiple-turn primary
winding is comprised of a ribbon conductor.
5. The transformer of claim 4 wherein the multiple turn primary
winding is comprised of a braided ribbon conductor.
6. The transformer of claim 4, wherein a conductive foil is used as
conductor for the windings.
7. The transformer of claim 1 in a series connectable distributed
active impedance injection module, wherein the active impedance
injection module is insulated from ground and at a high-voltage
transmission-line potential.
8. The transformer of claim 1 in a series-connectable distributed
active-impedance injection module, wherein distributed
active-impedance injection module is enabled to inject any of an
inductive or a capacitive impedance on to the high-voltage
transmission line, via the transformer, for line balancing and
control of power transfer.
9. An apparatus for injecting a voltage or impedance in series with
a high voltage transmission line comprising: an injection module
having; an injection transformer having a multiple-turn primary
winding and a multiple-turn secondary winding, the primary winding
being adapted for connection in series with the high-voltage
transmission line; the secondary winding being connected to a
converter; the converter being coupled to a controller for
controlling the inverter; and the secondary winding being connected
across a bypass switch for providing protection to connected
circuits.
10. The apparatus of claim 9 wherein the injection module is
contained in a housing supported by the transmission line, a
transmission line tower, or a special purpose tower.
11. The apparatus of claim 10 wherein the housing is insulated from
ground and is also virtually grounded to the high-voltage
transmission line.
12. The apparatus of claim 9 wherein the number of turns in the
primary winding is selected to reduce the operating voltage of
circuitry connected to the secondary winding, and to increase the
coupling to the high-voltage transmission line.
13. The apparatus of claim 12 wherein the number of turns in the
secondary winding is selected to reduce the operating voltage of
circuitry connected to the secondary winding to allow use of
off-the-shelf power electronic components.
14. The apparatus of claim 12, wherein the apparatus is enabled to
inject any of an inductive or a capacitive impedance generated by
the injection module on to the high-voltage transmission line, via
the injection transformer, for line balancing and control of power
transfer.
15. The apparatus of claim 9 wherein the injection module is
contained in a housing, the housing being supported by the
high-voltage transmission line, a transmission line tower or a
special-purpose tower, the apparatus being insulated from its
support.
16. The apparatus of claim 9 wherein the modules are also virtually
grounded to the high-voltage transmission line.
17. A method of providing distributed active-impedance injection
modules in high-voltage transmission-line systems comprising:
providing in each of a plurality of housings, a module having a
transformer core, a multiple-turn primary winding on the
transformer core, a multiple-turn secondary winding on the
transformer core and a converter; cutting a high-voltage
transmission line into segments; and splicing an end of each of a
pair of adjacent segments of the high-voltage transmission line to
a respective end of the multiple-turn primary winding of a
respective module; and supporting each housing by the transmission
line as spliced, by a high-voltage transmission line tower or by a
separate structure.
18. The method of providing distributed active-impedance injection
modules in high-voltage transmission-line systems of claim 17,
wherein the provided injection modules provide line balancing and
power flow control capability for the high-voltage transmission
line system by injecting active impedances onto the high
voltage-transmission lines onto which these are spliced.
19. The method of claim 17 wherein each housing is directly
suspended from a respective high-voltage transmission line tower by
at least one insulator.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 62/264,739 filed Dec. 8, 2015.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to systems and methods for
dynamic line balancing of high-voltage (HV) transmission lines
using spatially distributed active impedance injection modules that
are connected directly in series with the HV transmission lines
that form the HV electric power grid.
[0004] 2. Prior Art
[0005] HV electric power grids typically operate at voltages that
are on the order of about 50 kV up to about 600 kV. One of the
requirements of these HV power grids is the need for dynamic
distributed active power-flow control capability that can inject
both inductive and capacitive impedance on to the HV transmission
line as required to achieve line balancing and phase angle
correction. A system that can react fast to the problems of power
flow over the grid will greatly improve the grid operation and
power-transfer efficiency.
[0006] Congested networks limit system reliability and increase the
cost of power delivery by having part of the power dissipated in
unbalanced circuits causing loop currents with associated power
loss. In addition, substantially out-of-phase voltages and currents
on the transmission lines reduce the capacity of the lines to
transfer real power from the generator to the distribution
substation. To remove this limitation, it is desired to have HV
power grids with transmission lines that are balanced, with power
transfer shared substantially per optimization methods, with
reasonable power factor, and controllable phase difference between
voltage and currents. These improvements reduce the loop currents
and associated losses and enable real power transfer over the grid
up to the capacity of the lines.
[0007] Most of the grid control capabilities today are ground based
and installed at substations with switchable inductive and
capacitive loads. These installations require high-voltage
insulation and high-current switching capabilities. Being at the
substations these can use methods of cooling that include oil
cooling, forced recirculation of coolant, and other options without
consideration of the weight and size of the units. These lumped
controls require a centralized data collection and control facility
to coordinate operation across the grid and hence have associated
delays in implementing the control function on the power grid.
[0008] Distributed and active control of transmission line
impedance, if effectively implemented with high reliability,
improves the system efficiency substantially, but requires
cost-effective implementations that can alter the impedance of the
HV transmission lines, with fast identification and fast response
to line-balance issues, by changing the phase angle of the
current-voltage relationship applied across the line, thus
controlling power flow.
[0009] At present proven effective and reliable solutions for
distributed control of the power grid as, for example, described in
U.S. Pat. No. 7,835,128 to Divan et al (the '128 patent) are
limited. FIG. 1 shows a representation of the present-day
distributed line balancing system 102 using a "distributed series
reactor (DSR)" 100 using a passive impedance-injection module.
[0010] Power is transmitted from the electric power source or
generator 104 to the load or distribution substation 106. Spatially
distributed passive inductive impedance injection modules or DSR
100) are directly attached to the power conductor on the HV
transmission line 108, and hence form the primary winding of the
DSR 100 with a secondary winding having a bypass switch that, when
open, inject an inductive impedance on to the line for distributed
control. These DSR 100s only provide a limited amount of control by
injecting only the inductive impedance on to the line. When the
secondary winding is shorted by the bypass switch, the DSR 100 is
in a protection mode and injects substantially zero impedance on to
the HV line.
[0011] FIGS. 2 and 2A and 2B show embodiments of a passive
impedance injection module DSR 100. The HV transmission line 108 is
incorporated into the module as the primary winding by adding two
split-core sections 132 that are assembled around the HV
transmission line 108. The core sections 132 are attached to the HV
transmission line 108 with an air gap 138 separating the sections
after assembly. The air gap 138 is used to set a maximum value of
fixed inductive impedance that is to be injected on the HV line via
the primary winding. Secondary winding 134 and 136 encircles the
two split-core sections 132 and enables the bypass switch 122 to
short out the secondary winding and prevents injection of inductive
impedance on to the a HV transmission line 108 and also provides
protection to the secondary circuits when power surges occur on the
HV transmission line. The split core sections 132 and the windings
134 and 136 comprise the single-turn transformer (STT) 120. A power
supply module 128 derives power from the secondary windings
134&136 of the STT 120 either via the series-connected current
transformer winding 126 or via the alternate parallel-connected
winding. The power supply 128 provides power to a controller 130.
The controller 130 monitors the line current via the secondary
current of the STT 120, and turns the bypass switch 122 off when
the line current reaches and exceeds a predetermined level. With
the contact switch 122 open, a thyristor 124 may be used to control
the injected inductive impedance to a value up to the maximum set
by the air gap 138 of DSR 100.
[0012] When using multiple DSRs 100 connected on the HV
transmission line as in FIG. 1, the inductive impedance injected by
all the DSRs 100 on the line segments provides the total control
impedance. The main reason for the choice and use of inductive
impedance injection unit DSR 100 is its simplicity,
inexpensiveness, and reliability, as it does not need active
electronic circuits to generate the needed inductive impedance. The
value of the inductive impedance of each DSR 100 is provided by the
air-gap setting of the transformer core and not electronically
generated, and hence has fewer failure modes than if the same was
implemented using electronic circuits. The difficulty in
implementing and using electronic circuits for impedance injection
units that can produce actively controllable high impedance for
injection comprising both inductive and capacitive impedance is
multi fold. It includes achieving, the long-term reliability
demanded by electric utilities while generating the voltage and
current levels, that are needed to achieve effective active control
of the lines in the secondary circuit, while remaining within
reasonable cost limits for the module.
[0013] Distributed active impedance injection modules on
high-voltage transmission lines have been proposed in the past.
U.S. Pat. No. 7,105,952 of Divan et al. licensed to the applicant
entity is an example of such. FIG. 3 shows an exemplary schematic
of an active distributed impedance injection module 300. These
modules 300 are expected to be installed in the same location on
the HV power line as the passive impedance injection modules (or
"DSR" 100) shown FIG. 1. The active impedance injection module 300
does not perform the same functions. In fact the active impedance
injection module 300 does not have a gapped core 132 of FIG. 2B
that provides the fixed inductive impedance. Instead the inductive
or capacitive impedance is generated using the converter 305 based
on the sensed HV transmission line 108 current. Sampling the
secondary current by the series-connected secondary transformer 302
does the sensing of the magnitude of the line current. The sensing
and power supply block 303 connected to the secondary transformer
302 extracts the HV transmission-line current information and feeds
the controller 306. The controller based on the received input
provides the necessary commands to the converter 305 to generate
the required inductive or capacitive impedance to adjust the line
impedance. The value of the impedance in this case is not fixed but
can be made to vary according to the status of the measured current
on the HV transmission line. Hence the system using spatially
distributed active impedance injection modules 300 provides for a
much smoother and efficient method for balancing the grid.
[0014] In practice the active impedance injection modules 300s have
not been practical due to reasons of cost and reliability. In order
to inject the needed impedances on to the HV transmission line for
providing reasonable line balancing there is a need to generate a
significant amount of power in the converter circuits. This has
required the active impedance injection modules 300 to use
specialized devices with adequate voltages and currents
ratings.
[0015] The failure of a module in a spatially distributed
inductive-impedance injection-line balancing system using DSR 100
modules inserts a near-zero impedance (equal to the leakage
impedance) set by the shorted secondary winding or substantially
zero impedance on to the line. Failure of a few modules out of a
large number distributed over the HV transmission line does not
mandate the immediate shutdown of the line. The repairs or
replacement of the failed modules can be undertaken at a time when
the line can be brought down with minimum impact on the power flow
on the grid. On the other hand, for utilities to implement
distributed active line balancing, the individual modules must be
extremely reliable. These also have to be cost effective to be
accepted by the Utilities.
[0016] Power transmission line balancing circuits have been limited
to the use of delayed-acting heavy-duty fully-insulated oil-cooled
inductive and capacitive impedance injectors or phase-shifting
transformers prone to single-point failures, located at substations
where repairs of these failed units can be handled with out major
impact on power transfer over the grid.
[0017] As described above the use the specialized devices that can
handle the needed power with high reliability demanded by the
utilities at a reasonable cost has not been possible so far. There
is a need for such a capability for converting the grid to a more
efficient and intelligent system for power distribution. If it can
be established, it will have a major impact on the efficiency and
capabilities of the grid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The drawings are meant only to help distinguish the
invention from the prior art. The objects, features and advantages
of the invention are detailed in the description taken together
with the drawings.
[0019] FIG. 1 is a representation of a high voltage transmission
line showing distributed passive impedance injection modules
attached directly to the HV transmission line. (Prior art)
[0020] FIG. 2 is an exemplary block diagram 200 of an inductive
impedance injection module using a single turn transformer for
distributed inductive impedance injection on a HV transmission
line. (Prior art)
[0021] FIGS. 2A and 2B are exemplary schematics of the single turn
transformer used in the passive impedance injection module of FIG.
2. (Prior Art)
[0022] FIG. 3 is an exemplary block diagram 300 of an active
impedance injection module, licensed to the current entity, using a
single-turn transformer for distributed active impedance injection
on to a HV transmission line. (Prior Art)
[0023] FIG. 4 is an exemplary block diagram 400 of an embodiment of
the disclosed active impedance injection module using multi-turn
primary windings for distributed active impedance injection on a HV
transmission line.
[0024] FIG. 4A is an exemplary schematics of the multi-turn primary
transformer as per an embodiment of the current invention. The
multiple secondary turns are deliberately not shown in order to
provide a simpler drawing.
[0025] FIG. 4B shows an exemplary cross section of the multi-turn
transformer of FIG. 4A.
[0026] FIG. 5 is a representation of a high voltage transmission
line showing various ways the distributed active impedance
injection modules are to be supported while being directly attached
to the HV-transmission lines and operating at line voltage as per
the embodiments of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] As discussed above there is a need to have high-reliability,
fault-tolerant and intelligent distributed dynamic-control modules
(distributed active impedance injection modules) with capability to
inject both inductance and capacitive impedances of sufficient and
appropriate magnitude on to high-voltage transmission lines to
enable distributed power flow control. These distributed dynamic
control modules are directly attached to the HV-Transmission line
and are at line potential while in operation. The distributed
dynamic control modules are enabled to operate by extracting power
from the HV-Transmission line for control and for generating the
necessary voltages to be impressed on the High Voltage (HV)
transmission line. The modules generate voltages at the right phase
angle for injection on to the HV-transmission line, through the
multi-turn transformer, to provide the necessary inductive or
capacitive impedance during operation.
[0028] The invention disclosed the use of the multi-turn
transformer having multi-turn primary winding connected in series
with the HV transmission line 108 by cutting and splicing in the
winding. The secondary side of the multi-turn transformer and all
associated circuitry are electrically isolated from the ground.
However, one side of the secondary winding is connected to the
primary winding to provide a virtual ground or "floating ground"
reference and also partly to protect the secondary-side circuits
form stray fields. Alternately the virtual ground 408 can be
established by connecting the negative dc link of the
inverter/electronic injection module to the HV transmission line.
Further, both may be grounded for effective operation. Different
power-electronics topologies may necessitate other grounding
schemes and these schemes do not effect the key invention but,
rather, are specific implementations.
[0029] In order for the distributed control modules to be
successfully accepted by utilities and installed on lines, these
distributed control modules have to be smart and self-aware,
remotely controllable and configurable. The modules should be of a
reasonable weight compared to the line segment over which these are
to be installed, even where the modules are suspended in an
insulated fashion from the towers or are supported by additional
support structures. These should also have a low wind resistance to
reduce the effect of wind loading on the line/tower/special support
structure employed. As an essential feature all the electronic
components and circuits of the module should have very high
reliability to reduce the probability of line down times due to
failure of the modules/components used therein. The splicing
connection of the module to the HV transmission line also has to
have high reliability.
[0030] The invention disclosed provides distributed active control
having very high reliability and capability for power flow and line
balancing across the multiple high-voltage transmission lines used
for power transmission on the high power grid system. The invention
overcomes the issues of the prior art implementations discussed and
meet the criteria set for the use of the distributed control
modules that are discussed below.
[0031] There are multiple requirements that have been defined for
achieving the use of distributed control that need changes from the
prior art implementations. These are: [0032] 1. The need is to have
a distributed module that can generate and supply the required
range of inductive and capacitive impedances (generating the
necessary leading or lagging power) to the transmission line to
provide the necessary control for line balancing. [0033] 2. Provide
the above capability at a reasonable cost point-preferably by using
standard off-the-shelf power-electronics components; this means
that the secondary winding and associated circuits operate at
voltages and current levels normally seen in high-volume
power-electronic applications. Using off-the-shelf
power-electronics components means using general-purpose
power-electronics components that are also manufactured and sold in
the ordinary course of business for other uses. [0034] 3. The third
is the need for reliability of the distributed modules to be high
enough to eliminate failures and related line shut downs to an
acceptable level for the Utilities--this is achievable if standard
power-electronics components, with associated high reliability can
be used in the secondary circuits. [0035] 4. The final need is to
have relatively low weight and low wind-capture cross section for
the module to be attached to the HV-transmission line directly or
with minimum extra support.
[0036] The disclosed invention provides for improvement in all the
above aspects in the embodiments disclosed below:
[0037] The prior art dynamic injection modules had problems, which
prevented their acceptance. One was the need for specialized
components for the generation of the magnitude of injection power
(voltage and current) to be generated to provide adequate control
of the HV transmission line segment where the module is attached.
The second was the lack of reliability due to the modules handling
high power levels, which again necessitated specially tested and
qualified component use. Both the above requirements resulted in
the cost of the module also being very high for use by
utilities.
[0038] The disclosed invention for increasing the impressed voltage
or impedance on the transmission line uses multiple turns on the
primary winding of a series-connected injection transformer.
Increasing the number of turns in the primary winding alters the
turns ratio of the transformer, and allows the distributed active
impedance injection module (injection module) to have a greater
impact. Since the primary winding of the injection transformer need
to be in series with the HV transmission line, the use of
additional turns of the primary winding requires the HV
transmission line to be cut and the ends of the winding to be
spliced in series with the HV transmission line. Further having
multiple turns of heavy-duty wire, capable of carrying the line
currents seen on the power grid and the use of a heavier core to
provide the required coupling/flux linkage to the line, increases
the weight and wind-capture cross section of the injection module.
Though the injection modules are still attachable directly to the
line, it is preferable to provide additional support for the
heavier injection modules of the present invention due to its
additional weight.
[0039] The advantages of the disclosed multi-turn primary
transformer include the ability to inject higher voltages, with
90-degree lead or lag angle, providing inductive or capacitive
impedances respectively, on to the HV transmission line for power
flow control and grid optimization. With more turns, the
transformer can also be designed such that
the--power-rating-to-weight ratio (kVA per kg) of the unit can be
increased, increasing the economy of the unit as well. The use of
the multi-turn primary winding also allow the preferred use of
non-gapped transformer core, with high-permeability core materials,
thereby reducing the flux leakage and improving power transfer
between the primary and secondary windings. This, and the careful
selection of the number of secondary turns as a ratio of the
primary turns, further reduces the dynamic secondary voltages that
have to be generated for the required injection of voltages with
the correct phase for line balancing. The lower voltage required to
be generated across the secondary winding, to achieve the high kVA
injection, due to the carefully selected ratio of the primary to
secondary windings, enable high-volume power semiconductors and
components to be used. The use of these semiconductors and
components in the secondary circuit of the transformer (for the
control module, the power converter generating the necessary
leading or lagging voltages and protection circuits including the
shorting switch) make the module very cost-effective. Further the
use of lower voltages in the secondary circuits with associated
power electronic components with sufficient voltage margins provide
the necessary reliability of operation for these circuits connected
across the secondary windings to satisfy the reliability
requirements of the utilities for use of the distributed
modules.
[0040] Further using the distributed approach, with the impedance
injection modules, allows for significantly greater "N+X" system
reliability, where N is the required number of distributed modules,
and X is the number of extra redundant modules. Therefore, by
ensuring the reliability of each unit by itself being sufficient
for use by the utilities, the added extra redundant distributed
active-impedance control modules provide an additional layer of
"system" reliability over and above the unit reliability. The use
of these distributed impedance injection modules also provide the
intelligence at the point of impact, for providing fast response to
any changes in the optimum characteristics of the lines while
transferring power. This in turn results in a grid using
distributed injection modules of high reliability, capable of
providing very high system reliability, acceptable to all the
utilities. The use of the distributed impedance injection modules
hence are enabled to provide the best capability to balance the
power transmitted over the HV-transmission-lines of the power
grid.
[0041] FIG. 4 is an exemplary block diagram 400 of an
implementation of the active impedance injection module (injection
module) of the current invention. The injection module 400
comprises a multi-turn transformer 400A that has its primary
winding 403 connected directly to the transmission line 108 by
breaking the line and attaching the two ends of the primary winding
403, by splicing into the line segment as shown in FIG. 4A at 401
and 402. The primary winding 403, is in series with the HV
transmission line, 108 and carries the total current carried by the
transmission line, 108. In order to reduce losses due to skin
effect in the conductors and thereby reduce the heating of the
conductors used in the primary winding, 403 of the multi-turn
transformer 400A, a ribbon conductor or continuously transported
cable or a braided ribbon conductor may be used, instead of the
standard conductor, for the primary winding 403, as shown in the
exemplary cross section FIG. 4B of the multi-turn transformer,
400A. The ribbon/braided ribbon conductor when used, also helps to
reduce the over all weight of the conductor used and hence reduce
the weight of the whole injection module 400. A conductive foil may
also be used instead of the standard conductor in some cases to
reduce the weight and improve the current carrying capability. A
non-gapped transformer core 409, of high permittivity material, is
used to allow the maximum coupling possible between the primary
winding 403 and the secondary winding 404 of the multi-turn
transformer 400A. In this instance it is essential to have the
splicing system design to be made robust to withstand the stresses
that the splicing system will be subject to in the event of a
utility-level fault current and to the normal thermal cycles during
daily operation, to minimize the chance that splicing unit 401 and
402 failure will take down the line 108. The secondary winding 404
of the transformer couples to the primary winding 403 and is
floating with respect to the primary winding. An exemplary virtual
ground at the potential of the HV transmission line 108 is
established by connecting one side of the secondary winding of the
multi-turn transformer to the HV transmission line that enables the
injection module 400 itself to be floating at high voltage of the
HV transmission line 108 during operation.
[0042] A second low-voltage transformer 302 in the secondary
circuit is connected to a power supply 303 within the injector
module 400 that generates the necessary power required for the
low-voltage electronics comprising the sensing, communication and
control circuitry, all of which are lumped in the block diagram of
the module as controller 406, the voltage converter 405 and the
secondary winding shorting switch 304. The voltage converter or
simply converter 405 may be of any appropriate design, as such
devices of various designs are well known in the art. Typically
such devices are configured to inject an inductive load onto the
high voltage transmission line, and may also have the capability of
injecting a capacitive load on the transmission for power factor
control, and may further be capable of controlling harmonic content
in the high-voltage transmission line. Such devices are also known
by other names, such as by way of example, inverters or
converters/inverters. An exemplary device of this general type is
the combination of the inverter 71 and energy storage 74 of U.S.
Pat. No. 7,105,952, though many other examples of such devices are
well known. These devices typically act as active impedances to
controllably impose the desired impedance onto the high-voltage
transmission line. Also preferably the controller 410 used in the
preferred embodiments includes a transceiver for receiving control
signals and reporting on high voltage transmission line conditions,
etc.
[0043] The shorting switch 304 is activated to prevent damage to
the circuits connected across the secondary winding 404 during
occurrence of high transients on the HV transmission line due to a
short circuit or lightning strikes, or even for prolonged overloads
The controller 406 has sensor circuitry for monitoring the status
of the line and for triggering the protection circuits 304, and a
transceiver establishing a communication capability 410 for
inter-link communication and for accepting external configuration
and control commands, which are used to provide additional
instructions to the converter 406. The voltage converter 405 is an
active voltage converter that, based on input from the controller
406, generates the necessary leading or lagging voltages of
sufficient magnitude, to be impressed on the secondary winding 404
of the power line transformer of the distributed active impedance
injection module 400, to be coupled to the HV transmission line 108
through the series-connected multi-turn primary winding 403 of the
transformer. This injected voltage at the appropriate phase angle
is able to provide the necessary impedance input capability for
balancing the power transfer over the grid in a distributed
fashion. The multi-turn primary 403 of the disclosed transformer
400A coupled to the HV-transmission line 108 is hence the main
enabler for implementing the active distributed control of the
power transfer and balancing of the grid.
[0044] The current application addresses the advantages and
features of the use of multi-turn secondary windings 403 of a
distributed active impedance injection module (injector module) 400
attached to the HV transmission line 108. By using a multi-turn
primary winding 403 the multi-turn transformer 400A is able to
impress a higher voltage on the power HV transmission line with a
given transformer core size and weight while the connected circuits
of the secondary winding 404 (converter 405, controller 406 and
protection switch 304) of the transformer 400A are able to operate
at lower voltage ranges with the proper turns ration selection,
that are typical of power-electronics components commercially
available. This enables a cost-effective product using standard
components and devices while providing the needed high reliability
to the modules and high reliability to the grid system. The use of
this type of injection module 400 allows fast response to changes
in loading of the HV transmission lines at or close to the point of
change for dynamic control and balancing of the transmission lines.
By providing the capability for injection of sufficiently large
inductive and capacitive loads in line segments using reliable
distributed injector modules 400, the over all system stability is
also improved. The injector module 400 of the current invention is
not confined to substations, as in the past, but is enabled to
provide power flow control capability within existing utility
right-of-way corridors in a distributed fashion. The use of
multi-turn primary winding 403 also allows the typical use of
non-gapped core for the transformer improving the weight and power
transfer coupling of the device to the HV transmission line
108.
[0045] It should be understood that all the associated circuits of
the module are enclosed in a housing, which is suspended insulated
from ground at the HV transmission line voltage. Due to weight
considerations it is preferable to have these modules suspended
from the towers or provide additional support for their safe
attachment. FIG. 5 shows the typical attachment methods 500
possible for supporting the injection modules 400 connected to the
HV transmission lines 108. The on-line attachment 501, is the
typical prior art attachment used for the static modules, which
connects the module to the line directly, with no additional
support and lets the line supports take the weight of the module
and the line. Though this is acceptable, this type of attachment is
not the preferred one for the injection modules 400, of the current
invention. The preferred attachment for these impedance injection
modules 400, distributed for line balancing over the grid system,
are with additional support, directly connected by supporting
insulators 502 on the HV transmission towers 510 or by using
special support structures 511 with insulated supports 503 for
providing the additional weight carrying capability for the
distributed module. The above support methods also improve the
reliability of the structures and system during extreme climatic
disturbances.
[0046] Even though the invention disclosed is described using
specific implementation, it is intended only to be exemplary and
non-limiting. The practitioners of the art will be able to
understand and modify the same based on new innovations and
concepts, as they are made available. The invention is intended to
encompass these modifications.
[0047] Thus the present invention has a number of aspects, which
aspects may be practiced alone or in various combinations or
sub-combinations, as desired. Also while certain preferred
embodiments of the present invention have been disclosed and
described herein for purposes of exemplary illustration and not for
purposes of limitation, it will be understood by those skilled in
the art that various changes in form and detail may be made therein
without departing from the spirit and scope of the invention.
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